# Homework Help: Dynamics Polar Coordinates

1. Sep 9, 2010

### lax1113

1. The problem statement, all variables and given/known data

http://img138.imageshack.us/img138/4317/problem110.jpg [Broken]

2. Relevant equations

3. The attempt at a solution

Really I have no clue where to start on this guy. We did a problem sort of similar to this in class but we were given acceleration so we could use the form of

Vp = at $$\hat{u}$$

From there we could say that Vp = $$\dot{r}$$ $$\hat{u}$$r + r$$\dot{\theta}$$$$\hat{u}$$$$\theta$$ = at $$\hat{u}$$

I don't see how I could apply this equation in this problem, or really even if it does apply.
Any hints would be greatly appreciated, just to get a start in the right direction!

Last edited by a moderator: May 4, 2017
2. Sep 9, 2010

### Delphi51

Well, it looks interesting anyway!
I don't know what you mean by Vp . . .
Initially, r is just d and θ = 0 (the distance and angle from the origin).
I think finding dr/dt will require knowing r as a function of time so it can be differentiated. I would write out formulas for the x and y position of the the particle as a function of time as in a standard trajectory question, then calculate r and θ from them. There may be shorter ways.